&FIELD


overview

  The instructions of the field section fall in 4 categories:

  - setting various parameters
  - plotting and printing
  - understanding the field
  - service instructions

  The use of this section is fairly straight-forward since there is only
  one frequently used instruction in this section: PLOT.

  ------------------------------------------------------------------------
  Setting parameters:
  ------------------------------------------------------------------------
  AREA                       Sets the view and size of the plotting area
  GRID                       Sets the density of the plotting grid
  SELECT                     Establishes the list of sense wires
  TRACK                      Sets the track used for graphs

  ------------------------------------------------------------------------
  Plotting and printing:
  ------------------------------------------------------------------------
  PLOT                       General purpose field plotting instruction
  PRINT                      General purpose field printing instruction

  ------------------------------------------------------------------------
  Understanding:
  ------------------------------------------------------------------------
  CHECK                      Verifies charges and boundary conditions
  MULTIPOLE-MOMENTS          Computes the multipole moments for a wire

  ------------------------------------------------------------------------
  Service instructions:
  ------------------------------------------------------------------------
  SAMPLE                     Field value (see also CALL ELECTRIC_FIELD)
  TIME                       Times the field calculations

  Note 1: there are several instructions in the optimisation section that
          perform related tasks.
  Note 2: there are also procedure calls that perform related tasks:
          ELECTRIC_FIELD, ELECTRIC_FIELD_3, INTEGRATE_CHARGE,
          INTEGRATE_FLUX and MAP_INDEX.


AREA

  Sets the part of the chamber that is being looked at, and
  optionally also sets the projection.

  AREA commands are found in several sections:
  - field section: where the command establishes the plane on
    which e.g. contours are plotted
  - drift sections: where the command limits the region over
    which particles are allowed to drift and sets the viewing
    direction for plots of drift lines
  - optimisation section: shares both the field and the drift
    area, respectively to set the optimisation plane and to
    limit drift lines
  - signal section: shares the drift area

  The geometrical aspects of the field and the drift area are
  distinct, but the viewing plane is shared between the two.

  Format:

  AREA [xmin ymin xmax ymax | xmin ymin zmin xmax ymax zmax] ...
       [VIEW plane] ...
       [ROTATE angle] ...
       [X-Y | R-PHI | X-Z | Y-Z | 3D | CUT] ...
       [LIGHT-ORIGIN phi_light theta_light] ...
       [REFLECTED-FRACTION frac_refl] ...
       [SCATTERED-FRACTION frac_scat] ...
       [PARTIAL-BOX-TICKMARKS | FULL-BOX-TICKMARKS] ...
       [PARTIAL-TUBE | FULL-TUBE] ...
       [PARTIAL-PLANES | FULL-PLANES] ...
       [SPLIT-INTERSECTING-PLANES | NOSPLIT-INTERSECTING-PLANES] ...
       [NOSORT-PLANES | SORT-PLANES] ...
       [OUTLINE | NOOUTLINE] ...
       [PLOT-MAP | NOPLOT-MAP] ...
       [NOSTEP | STEP]

  Example:

  AREA -1 -1 1 1

Additional Information on:

  • geometry
  • X-Y
  • X-Z
  • Y-Z
  • R-PHI
  • CUT
  • 3D
  • plane
  • plane_coordinates

  • angle

      If the default coordinate axes in the viewing plane (see the
      topic "plane_coordinates") do not suit you, then you can rotate
      these axes by an amount you specify with this keyword.
    
      The angle should be specified in degrees.
    
      [Default rotation angle: 0 degrees.]
    

    Additional Information on:

  • light
  • FULL-BOX-TICKMARKS
  • FULL-PLANES
  • FULL-TUBE
  • SPLIT-INTERSECTING-PLANES
  • SORT-PLANES
  • OUTLINE
  • PLOT-MAP
  • STEP

  • CHECK

      (Mainly a debugging instruction.) Checks the field calculations.
      The WIRE option, however, is often used to determine the field
      at the surface of the wires - since this determines to a large
      extent the avalanche amplification.
    
      Format:
    
      CHECK [WIRES] ...
                 [EPSILON-WIRE eps_wire] ...
            [CHARGES] ...
            [PLANES] ...
            [TUBE] ...
            [MAXWELL] ...
                 [BINS bins] ...
                 [EPSILON-MAXWELL eps_Maxwell] ...
                 [PRINT | NOPRINT] ...
                 [PLOT | NOPLOT] ...
            [FULL] ...
            [NOKEEP-RESULTS | KEEP-RESULTS]
    
      Example:
    
      CH WIRE BINS 50
    
      (This would be used to find the field on the surface of the wires
      and you'll get a few checks on the wire-charges for free.)
    

    Additional Information on:

  • bins
  • eps_Maxwell
  • eps_wire
  • FULL
  • MAXWELL
  • PLANES
  • TUBE
  • WIRES
  • CHARGES
  • KEEP-RESULTS

  • GRID

      Sets the number of grid points in x (or r) and y (or phi) used
      to produce the plots and tables. [Default is 25 for both.]
    
      The second arguments may be omitted in which case the first value
      will be used for both the x (or r) and the y (or phi) spacing.
    
      Format:
    
      GRID  number_of_steps_in_x  [number_of_steps_in_y]
    
      Example:
    
      GRID 50
    

    MULTIPOLE-MOMENTS

      Helps in finding wires that have a clear dipole, quadrupole etc
      moment because of the presence of other wires nearby. Such wires
      should receive special attention because Garfield assumes that
      a simple charge is enough to describe the wire.
    
      The absence of dipole, quadrupole etc potentials in Garfield is
      not a fundamental limitation. Such potentials can be added on
      request.
    
      Format:
    
      MULTIPOLE-MOMENTS ...
           WIRE wire ...
           [ORDER order] ...
           [RADIUS r] ...
           [NOPLOT | PLOT] ...
           [NOPRINT | PRINT] ...
           [EPSILON eps] ...
           [ITERATE-MAXIMUM iter]
    
      Example:
    
      MULTIPOLE WIRE 1 PLOT
    
      Will plot the multipole moments up to order 4 for wire 1.
    

    Additional Information on:

  • wire
  • order
  • r
  • eps
  • iter
  • PLOT
  • PRINT

  • OPTIONS

      Enters global and local options. Only the local options are
      listed here.
    
      Format:
    
      OPTIONS  [NOCHECK-MAP-INDICES | CHECK-MAP-INDICES] ...
               [CONTOUR-ALL-MEDIA | CONTOUR-DRIFT-MEDIUM]
    
      Example:
    
      opt check-map contour-drift
    

    Additional Information on:

  • CHECK-MAP-INDICES
  • CONTOUR-ALL-MEDIA
  • CONTOUR-DRIFT-MEDIUM

  • PLOT-FIELD

      This instruction plots the electrostatic and magnetic field in a
      variety of ways.
    
      CPU time can be saved if several plots are combined in a single
      command.
    
      Similar instructions exist in the drift and signal sections.
    
      Format:
    
      PLOT-FIELD [CONTOUR [f1]   [RANGE {cmin cmax | AUTOMATIC}] ...
                                 [N n] ...
                                 [LABELS | NOLABELS] ] ...
                 [GRAPH [f2]]    [ON f_curve] ...
                                 [N n]] ...
                                 [SCALE min max] ...
                                 [NOPRINT | PRINT] ...
                 [HISTOGRAM [f3] [RANGE {hmin hmax | AUTOMATIC}] ...
                                 [BINS nbin]] ...
                 [SURFACE [f4]   [ANGLES phi theta]] ...
                 [VECTOR [f5 f6 [f7]]]
    
      If you don't manage to fit all this on a single line, remember
      that lines that end on an ellipsis are continued on the next.
    
      Examples:
    
      PLOT HIST VECTOR SURF CONT
      PLOT CONTOUR RANGE 500 550
      PLOT GRAPH 'SIN X'
    
      (The first example makes most of the plots using default functions
      and ranges - useful as a first call. The second example makes a more
      detailed contour plot and the third one shows that you can use this
      program also to produce graphs of arbitrary functions.)
    

    Additional Information on:

  • contour
  • graph
  • histogram
  • surface
  • vector
  • functions

  • PRINT

      Prints a table of a series of field functions (using X, Y or R, PHI and
      EX, EY or ER, EPHI plus BX, BY, Bz if applicable as symbolic names). A
      large number of functions may be given as argument but the tables are
      always for at most 4 functions at the time. This instruction tends to
      produce a lot of output: (GRID/10)**2 pages.
    
      Format:
    
      PRINT f1 f2 ...
    
      Example:
    
      PR EX, EY, E, V
    

    SAMPLE

      Evaluates and prints the field at a single point.
    
      This instruction was used for debugging - but is now superseded
      by the procedure call ELECTRIC_FIELD and ELECTRIC_FIELD_3.
    
      Format:
    
      SAMPLE x y
    
      Example:
    
      SAMPLE 0.5 0.5
    

    SELECT

      Selects and groups the sense-wires. The grouping is of no importance in
      this section. The selection determines which wires are checked by CHECK.
      The argument string consists of wire-codes and/or wire-numbers.
    
      Format:
    
      SELECT wire_selection
    
      Example:
    
      SEL (1 S) 2 F
    
      (Put wire 1 together with all S wires in one group, make wire 2
      a group of its own and do the same for each of the F wires.)
    

    TIME

      Times the field evaluation n [default: 1000] times.
    
      Format:
    
      TIME [n]
    
      Example:
    
      TIME 10000
    

    TRACK

      Defines the track used by the PLOT GRAPH instruction.
    
      Format:
    
      TRACK x_start y_start x_end y_end
    
      Example:
    
      TR -1 -1 -1 1
    

    Keyword index. Formatted on 10/11/98.